This invention relates generally to sealed trays for storing food products, and more particularly to a tray and lid assembly for a pre-cooked meal which makes it possible to store the meal in the frozen state and to thereafter reheat the meal to a service temperature level without degrading its basic texture, flavor and nutritional qualities.
To meet the growing need for quickly-prepared, low-cost meals, convenience food operations have been developed in which the food to be served is first cooked and then stored in the cold or frozen state. When an order is placed for a particular item on the menu, the selected item is withdrawn from the freezer, the frozen pre-cooked meal is then thawed and reheated.
In reheating a pre-cooked frozen meal in homes, restaurants and other facilities, it is difficult, when going from the frozen state to an adequately heated service condition, to avoid a situation in which the core of the product is still cold even though the outer layer is quite hot. And when one seeks to ensure that the body of the food is hot throughout, there is a tendency to overheat the meal and thereby re-cook it, with a resultant loss of nutritional value and flavor.
In my related U.S. Pat. No. 4,112,916, "Hot Air Oven For Food-Loaded Cartridges," and in the above-identified patent applications, there is disclosed a convenience food service technique in which pre-cooked meals which have been refrigerated and stored may be thereafter reheated and made directly available to customers, the technique being such that the essential flavor, texture and nutritional qualities of the meal as originally cooked, are substantially retained in the recooked meal.
In the apparatus disclosed in my prior patent and patent applications, the pre-cooked meal is placed in a tray covered by a lid. The concern of the present invention is with a tray and lid assembly for a pre-cooked meal which takes into account the varying temperature conditions to which the meal is subjected and which hermetically seals in the meal only when the need for a seal is dictated by the technique.
Thus when the pre-cooked meal is first placed in the tray and covered by the lid, and the covered tray is then placed in a refrigeration chamber to freeze the meal, it is essential at this point that the tray be effectively sealed to prevent the infiltration therein of humid air and airborne bacteria. When, however, the covered tray containing the frozen meal is thereafter placed in an oven of the type disclosed in my prior patent and patent applications to reheat the meal to a service temperature level, it is essential in the initial course of heating when the air within the covered tray is being heated and expanded, that the covered tray be vented to relieve the expanding air. Otherwise, the resultant air pressure may cause the sealed tray to explode. But once the expanding hot air has been expelled from the covered tray, it is desirable to again seal the tray so that moisture and volatile oils in the food being heated are not discharged but are retained.
Clearly, therefore, a tray and lid assembly which remains unsealed regardless of whether the food is being frozen or heated will not satisfy the requirements of the technique, nor will an assembly which is always sealed; for in neither case will the assembly, when necessary, allow air to escape from the covered tray.